Radio navigation system



July 6, 1943. w. P. LEAR 2,323,337

RADIO NAVIGATION SYSTEM Filed Jan. 11, 1940 4 Sheets-Sheet 1 f J 1AUTOMATIC RADIO M 9 I a DIRECTION FINDER ATTORNEY.

[(7 j INVENTOR.

July 6, 1943. w. P. LEAR 2,323,337

RADIO NAVIGATION SYSTEM File d Jan. 11, 1940 4 Sheets-Sheet 2 INVENTOR.zz/AM- [5,45

BY Wdm ATTORNEY.

July 6, 1943. w. P. LEAR 2,323,337

RADIO NAVIGATION SYSTEM Filed Jan. 11, 1940 4 Sheets-Sheet 3 INVENTOR.W/[ZM/V R AfA/F ATTORNEY.

July 6, 1943. w. LEAR 2,323,337

RADIO NAVIGATION SYSTEM Filed Jan. 11, 1940 4 Sheets-Sheet 4 I INVENIOR.W/ZZ/M/ K 164/? BY I W & M

ATTORNEY.

Patented July 6, 1943 UNITED STATES PATENT OFFICE 13 Claims.

This invention relates to navigatiorxtl indication systems, and moreparticularly relates to a novel composite indicator directly solving andsimplifying heretofore complex problems in aircraft navigation.

The trend of modern aircraft navigation is towards greater safety andreliability of operations and schedules as well as towards greaterflexibility of maneuvering. Efforts have been directed to provideindications to effectively guide the pilot in his navigation despitedimcult terrain or adverse weather conditions such as Wind, rain, fog,and the like. The art, however, has developed complex systems for thesepurposes, requiring correlation of a number of separate indications,interpretations, and numerical calculations on the part of the alreadyburdened pilot, as well as requiring a multitude of special ground radioand associated equipment. 1

In accordance with the present invention, aircraft navigation is reducedto simple terms, continuously affording the pilot automatic pictorialindications of his orientations and maneuvers, and reducing even themost advanced problems to simple, readily interpreted indications. Thepilot is thus relieved of mental strain and uncertainty as to positionor orientation, and is directly apprised of the best and most directmanner to navigate his aircraft under all conditions of flight. The onlyground facility required in conjunction with the system of the inventionis a single radio transmitter, of any type, in the vicinity or in thepath of the destination.

With the system of the present invention, straight-track navigationalong any desired radial heading is readily effected towards or awayfrom a radio station, despite cross -winds or non-visibility. The angleof drift of the aircraft due to cross-winds is directly indicated, andautomatically corrected for in flight. The composite instrument may beused as a regular 360 automatic radio direction finder and as agyro-compass. With the system the pilot is enabled to confidentlyexecute a direct low approach and blind descent onto a runway,regardless of local weather conditions. For blind landing, thetransmitter is located at the head of the selected runway.

The composite navigational indicator comprises a course index heldangularly fixed in space parallel to the destination of the desiredcourse, and an index giving an accurate bearing on a radio station inthe path of the desired course. A further reference index is providedcorresponding to the zero heading or lubber line of the aircraft. Thedesired course index is continuously oriented with a directionalgyroscope or gyro-compass, or with a magnetic compass. The "radiocourse" index is controlled by a 360 azimuthally compensated automaticradio direction finder system tuned to the charted ground radiostation.' The composite navigational indicator accordingly performs thefunctions of a radio direction finder and a directional compass, as wellas the important additional functions referred to above and to bedescribed in detail hereinafter.

An important feature of the present invention resides in the provisionof means permitting the A pilot to adjust the desired course index ofthe instrument without opening it up. This feature is direct, saves timeand effort on the part of the pilot, and is particularly important wherean airdriven gyro-compass is incorporated with the indicator. The radiocourse index is inscribed on a transparent gear floatingly arranged in amanner preventing its freezing in position due to the presence ofnegative air pressures within the indicator instrument. The floatinggear is directly driven by the automatic radio direction finder system,being coupled to the azimuthal indicator thereof. A further importantfeature of the present invention resides in the direct novel pictorialarrangement of the composite indications, resulting in theirinterpretation by the pilot practically by intuition.

It is accordingly an object of the present invention to provide a novelcomposite navigational indication system.

A further object of the present invention is to provide a novelnavigational indicator directly resolving navigational problems intosimple terms.

Still a further object of the present invention is to provide a novelcomposite pictorial arrangement of navigational indications.

A further object of the present invention is to provide a compositepictorial navigation indicator combining 360 radio directional bearingswith an tion will become more apparent in the following description ofexemplifications thereof illustrated in the drawings, in which:

Fig.1 is a diagrammatic arrangement of a preferred embodiment of thenavigational system of the invention.

Fig. 2 is an elevational view, partly in section, of one form of thenavigational indicator.

Fig. 3 is a plan view of a slightly modified form of the navigationalindicator.

Fig. 4 is a diagrammatic blown-up illustration of the essentialcomponents of the navigational indicator of the invention.

Fig. 5 is an enlarged sectional view through the arrangement formanually setting the course index of the indicator.

Fig. 6 shows a modified arrangement for setting the course index of theindicator.

Fig. 7 is a cross-sectional view through the directional disk continingthe desired course index.

Fig. 8 illustrates a modified arrangement for the navigational indicatorsystem.

Figs. 9 to 14 illustrate some indications occurring in practice on thenavigational indicator.

Figs. 15, 16 and 17 are diagrammatic representations of typicalnavigational maneuvers as executed by an aircraft using the system ofthe present invention, and corresponding indications on the indicator.

A preferred arrangement which the system of my present invention mayassume in practice is diagrammatically illustrated in Fig. 1. The radiodirection finder section of the system gives automatic indications over360 degrees, and may well be the one disclosed in my copendingapplication, Serial No. 286,733, filed July 27, 1939, now Patent No.2,308,521, issued January 19, 1943, entitled "Automatic radio directionindicator." Equivalent automatic direction finders, capable of operatinga bearing indicator over a 360 scale and give a bearing on a tuned-inradio station, may instead be used. The illustrated direction findercomprises a radio receiver and control circuit unit indicated at I, towhich is connected non-directional antenna 2 and rotatable directionalor loop antenna 3 through leads 3'. A streamline housing about loopantenna 3, indicated in dotted lines at I, is used to reduce theaerodynamic drag of the loop antenna when mounted exterior of theaircraft. Earphones 5 are connected to direction finder unit I forcontinuous aural reception, useful for identifying the radio stationtuned-in and for obtaining weather reports or landing instructions.

A reversible motor 8 is connected to the control circuit portion ofdirection finder unit I through leads 6, and is energized in accordancewith the received radio signals to rotate in either direction inaccordance with the sense of the radio signal as determined by the loopantenna 3 when off-null position with respect to the incoming radiosignal waves. -The circuits and theory of this operation is described inPatent No. 2,308,521. Motor 6 is coupled to drive loop antenna 3 throughelectromagnetic clutch 1 electrically connected in parallel with motor8; re-

duction gearing 8; worm gearing 9; and quadrantal corrector unit I0interposed between shafts s and s for loop antenna 3.

Quadrantal corrector unit I0 is an important component of the system. Itis used for compensating for non-symmetrical metallic surroundings aboutthe loop antenna, which otherwise would cause false bearing indications.A suitable quadrantal corrector for the unit indicated at I0 isdisclosed in my Patent No. 2,296,285 and my copending application SerialNumber 344,854, filed on July 11, 1940, entitled Quadrantalcompensators." An azimuthal or bearing indicator for the directionfinder is indicated at H mechanically coupled to the gear systems 8 and9 of the loop antenna drive through flexible cable i2. points out theangular position of the tuned-in radio station. This position directlycorresponds to the angular position which loop antenna 3 assumes underthe action of motor 6, and as compensated by corrector unit In.

The composite navigational indicator is shown at 15. It is mechanicallycoupled to loop antenna 3 through flexible mechanical cable It directlyconnected to gearing 8 and indicator II. The indicator I 5 is shown inperspective in Fig. l; in elevation and partly in section, in enlargedFig. 2; in slightly modified plan view, in Fig. 3; and as a diagrammaticblown-up view, in Fig. 4. Indicator I5 is mounted in the cockpitadjacent the pilot with its scales preferably arranged horizontally.Navigational indicator i5 embodies a directional gyroscope orgyro-compass arranged to maintain directionalscale l 6 in predeterminedorientations. Directional scale it is graduatedin 360 degrees,'andrepresents the land reference scale of the composite indicator.

A caging knob i1 is coupled to the internal gyro-compass mechanism forperiodically resetting directional scale l6 to correspond with themagnetic compass readings. The reading of gyro-scale i6 as referred tothe zero index of indicator i5 is made identical with the reading, indegrees, of the magnetic compass in the aircraft. True course bearings,with respect to North as ascertained from a map, are correlated with themagnetic compass readings and therefore with the gyro-scale i6 readingsby taking into account magnetic variations, easterly or westerly, andmagnetic deviations of the magnetic compass, as will be set forthhereinafter. A desired course" index i8 is marked upon disk 26 which isadjustably mounted with respect to gyro-scale l6. Disk 26 is reset bypush-button l9 operated in conjunction with caging knob H in a manner tobe described. A "radio course" index 20, 21' is marked on transparentgear 28 mounted above directional scale l6 and desired course index i8.Radio index 20, 20 is directly controlled by flexible cable l4; and ismoved in exact correspondence with needle I 3 of azimuthal indicator II,and with loop antenna 3 operated through quadrantal corrector Ill.

The gyro-compass mechanism is contained within cylindrical housing II.It is preferably an air-driven type. A tube 22 projects from housing 2|for connection to a vacuum source to drive the gyroscope mechanism, notshown but well known in the art. An air filter 23 is used to purify thedrawn-in air. The 360 gyroscale' 8 6 is preferably etched directly onhorizontal turn-table 24. Tum-table 24 is connected to vertical shaft 25extending from the gyro-compass mechanism. Gyro-compass units per se arewell known in the art, and may take optional forms. Details thereofaccordingly not shown in the drawings. The directional gyroscope isarranged to maintain the orientation of tumtable 2t fixed in a set-updirection, regardless of changes of attitude of the aircraft or ofcasing 2i.

Shaft 28 of tum-table 2t may for example be connected to the verticalring of the gyro-com- Indicator needle l3 of indicator pass, not shownin the drawings, but indicated as within casing 2|. The horizontaltum-table 24 driven by the gyro-compass unit, and th associated cagingarrangement I! corresponds to the airport orientator instrumentmanufactured by the Sperry Gyroscope Company, Inc. of New York anddescribed and illustrated in their publication entitled AirportOrientator," dated ctober, 1938. The caging mechanism for controllingthe relative setting of turn-table 24 with respect to the zero index ofindicator I5, is operated by caging knob l1 directly geared, to thecontained gyro-compass mechanism. Suitable caging mechanisms are, forexample, shown in the gyro-compasses disclosed in U. S. Patent No.2,052,866 to Carlson et al. on September 1, 1936, for Pilot directinggyroscope, and No. 2,061,894 to Carlson on November 26, 1936 for"Constrained directional gyroscope. The term caging is used in its usualtechnicalsense and refers to the action efiected by the caging mechanismreferred to through caging knob I! to mechanically reset thegyro-compass so that its indications are manually adjustable. Inoperation, the caging mechanism holds the directional gyroscope uprightwhile the card is mechanically reset. When the caging knob H is pulledout in the directional gyroscope embodiment disclosed, the cagingmechanism inside is released leaving the gyroscope horizontal and free.

Disk 26 is marked with desired course index l8. Disk 25 is adjustablymounted centrally of turn-table M with a suitable clip or eyelet it. Theperiphery of disk 26 contains teeth t for engagement with toothed bar27. A desirable pitch for teeth t is 32 per inch, but a different pitchmay be used. Bar 271 is directly connected to push-button it at theexterior of easing ti, and is normally mechanically biased out ofengagement with the teeth of disk 26 by spring iii.

The radio course index 2%, db is inscribed on the transparent gear 28meshing with worm it coupled to mechanical shaft Ml. The radio courseindex preferably comprises a luminous head it and a luminous tail 2% asindicated, surfaced with a radium compound. The portions 2t, it of theradio course index are interconnected by two parallel lines 3t, 3tspaced sumciently to enclose desired course index bar it; whensuperimposed thereover, to afford the pilot a direct indication of suchcoincidence without incurring parallax. Parallel lines 3%, illi may beinscribed on gear 285 but ar preferably wires suitably set into thegear. Transparent cover 311 of navigational instrument it contains theaircraft reference index or lubber line lid, fixedly pointing to thezero index of scale 33. A picture 3% of an aircraft is aligned withlubber line 32 to give a direct pictorial representation of the aircraftreference index for ready interpretation of the composite indications ofthe instrument. Scale 33 is calibrated in degrees, equally from eitherside of 0 to assist the pilot in setting desired course index it, inamanner to be described.

Transparent cover it! of the instrument is sealed into the rigidmetallic lid 35 to prevent air leakage around its edges. A rubber gasket36 is mounted at the top inside surface of housing 2|]. Lid 35 isclamped against gasket 36 by bolts opening 39. Opening 99 preventsfrictional interference or freezing of therotation of gear '28 due tothe vacuum exerted on the gyro-compass unit within the instrument.

A preferred material for the radio course gear 28 containing index 20,20' is the transparent plastic commercially known as Lucite." The gearteeth 28"0! gear 28 may be molded into its periphery or, preferably,directly out thereon on a lathe. The opening 39 of gear 28 permits theproper mounting thereof on a mandril of a lathe, for cutting the teeth28' therein. Worm 29 is rotatably mounted in extension 40 of lid 35, andmeshes with floatingly mounted worm gear 28. The respective componentsof the indicator I5 are designed and constructed to prevent air leakageinto the instrument except through the filter provided at 2'3.

Fig. 5 is a cross-sectional view through the mechanism for manuallylocking the position of course disk 26 for use in adjusting desiredcourse index l8 with respect to gyro-scale l6. Bar 21 is slidablymounted in housing M of the instrument and is spring biased outwardly,away from teeth t of disk 26 by spring IS. A packing gland 4| surroundsrod 42 integral with bar 21, sealed off by packing nut 43 to prevent airleakage thru the mechanism. When push-button i9 is pressed againstspring iii, the pointed tip of bar 21 engages a tooth of toothed disk26, to hold disk 2d fixed against rotation. Desired course" index it isthen adjusted to point opposite the required angle on gyro-scale It bymanually rotating turn-table M. In the illustrated embodiment,turn-table M is rotated through caging knob-5H. The desired course angleis calculated to account for magnetic variations of the vicinity andmagnetic deviation of the compass. When desired course index it isproperly adjusted with respect to scale it, caging knob W is moved toits normal operating position and push-button i9 is released todisengage bar 2? from disk 26. The disk 26 arresting, and index Mladjusting, means is an important feature of the present invention. Itpermits the ready adjustment of the desired course index It by the pilotduring flight without opening up the navigational instrument.

Fig. 6 illustrates a modified arrangement for the course disk it lockingmechanism, operated electromagnetically rather than mechanically,eliminating the requirement of a packing gland. Pointed bar 2? isarranged to engage a tooth of toothed disk 2b, as in Fig. 5. A plungert2 joins with an extension of bar 2i, and is surrounded by solenoid d5.Spring-biased push-button 36 contains a metallic face arranged toelectrically close the circuit between contacts t8, t8 and com- -pletethe circuit to an energizing source, not

shown, connected to leads #9. When button lt or machine screws 3?through projecting lugs noid 45 is energized and moves plunger M to theright against its biasing spring 50, causing the tip of bar 21 to engagea tooth t of disk 26 and hold the disk against rotation for the settingof desired course index it. The components of the electromagnetic disklocking means are sealed into housing 2| to prevent air seepage into theinstrument.

The desired course index it has preferably a luminous bar arranged on ametallic disk 26 in the manner shown, composed of a phosphorescent orluminous material, such as a radium compound used in instrument marking.Fig. '7 is a cross-section through a preferred construction forthe"desired course disk 28 illustrating an undercutting or groove 55therein. Groove 55 is filled-in with the luminous compound to form thedesired course index l8. To avoid unbalancing of the turn-table 24 andefiect undesirable precession in the operation of the gyroscope, asimilar mass of luminous material is arranged symmetrically oppositeindex l8 on the reverse side. A corresponding groove 55' is cut in theunder surface of disk 26, of the same size and shape as groove 55 and isfilled-in with the luminous compound to form compensating index i8.Absorption of moisture by the luminous compound during humid weather isthus compensated for weight increase at diametrically opposite sides ofthe center of rotation of turn-table 2!. Precession effects are thusbalanced out.

Changes in the specific forms of the illustrated exemplifications of theinvention may be made without departing from the broader spirit andscope thereof. The radio course gear and associated index 20, 20' may,for example, be mounted exterior of the navigational unit. Differentforms of the arresting means for desired course disk 26 may be employed.Diiferent automatic radio directional receivers may be used to drive the360 radio course index 20. Other means for spatially orienting thecourse disk 24 and the desired course index it may be incorporated inthe system besides the directional gyroscope. In place of thedirectional gyroscope or gyro-compass disclosed for operating turn-table24, a magnetic compass may be used with the operating member of themagnetic compass indicator being coupled to turn-table 2 1 or itsequivalent. Such magnetic compass drive arrangement is disclosed in mycopending application, Serial No. 335,229 filed on May 15, 1940.

The gyro-compass or magnetic compass unit may be separated from thecomposite indicator arrangement with telemetering or repeater means.Fig. 8 illustrates such modification of the invention, useful in certaincommercial ap-.

plications. The composite indicator is shown at 60, containing thescales and relative components as illustrated in Figs. 3 and 4, includesdesired course index I8 on, adjustable disk 26; radio course index 2U,20, (on transparent gear 28); 360 directional scale IE, (on turn-table24); and lubber line" 32 together with airplane pic-. ture 34, (ontransparent cover 3!). The radio course index 20, 20 is mounted on thetransparent gear 28 which meshes with a worm rotatably supported inextension 40 of the casing of composite indicator 60 in turn directlycoupled to flexible cabl H which leads directly to and is controlled byan automatic direction finder such as shown in Fig. 1. Push-button I9and bar 21 are similar to those shown in the previous modifications, asa means for manually setting the desired course" index l8 withoutopening up indicator 60.

The course disk orientation mean, specifically a directional gyroscope,is contained at SI for remotely controlling the orientation ofhorizontal scale It and its associated desired course" index iii. Amagnetic compass may be used in place of the gyro-compass. Compass unit6! contains the usual gyro-compass (or magnetic compass) scale 62, andin the illustrated case contains an inclinometer'63. A caging knob 66 isused to control the position of directional scale 62, and as will beshown, the corresponding position of scale l8 and desired course" indexll.

A telemetering arrangement synchronizes the movements of scale 62 withthat of scale It of composite indicator 60. The transmitter of thetelemetering system is indicated at 65 on top of compass unit 6|. Apreferred telemetering system is the Selsyn direct current type,energized by battery 66. Movement in transmitter 65 is mechanicallyeffected by the motivating means for scale 82 corresponding, forexample, to vertical shaft of Fig. 2. Th translator for the Selsynsystem is incorporated within the housing of composite indicator 60, andis electrically interconnected with Selsyn transmitter 65 by three-wirecable 81. The direct current Selsyn telemetering system used is similarto the one disclosed in Figs. 1 and 10 of my Patent No. 2,308,521. Othertelemetering means between directional scales l6 and 62 may b used.Desired course index it may be reset with respect to scale it ofindicator 60 by pressing button I 8 to cause bar 21 to engage a tooth ondisk 2|,

and operating caging knob 64 to turn scale it by remote control.

- Aircraft navigation with the composite indicator The compositenavigational indicator of the present invention automatically andaccurately informs the pilot by pictorial indications how bets tonavigate the aircraft under all conditions of flight. Problems inaircraft navigation are directly resolved, relieving the pilot of mentalstrain, calculations and uncertainty. The indications are quickly andeasily interpreted, reducing the most advanced navigational problems tosimple terms. With the system, a pilot can readily fly blind along ,anydesired radio course, heading towards or away from any radio station inany desired radial direction, and traveling a predetermined straighttrack over the ground regardless of wind force or direction. The angleof drift or crab of the aircraft due to cross-winds is directlyascertained by the indications, and automatically corrected for inflight. Th composite instrument of the invention serves as the usualdirectional gyroscope or gyro-compass in the aircraft, thus eliminatingthe installation of a separate one. The automatic uni-directional 360radio course indicator incorporated in the system may be usedindependently as such for homing, and radio directional flight ingeneral. A distinct indication is obtained when the aircraft passes overthe radio station by a 180 reversal of the radio course" index 20, 20'.Th system is also most advantageously used for effecting a low approachand blind landing on a selected runway.

Only a single ground radio transmitter station is necessary fornavigation with the instrument of the invention. The largest airliner,bomber or clipper may be navigated on a straight-track to anyout-of-the-way airport having a simple radio transmitter and safelyblind-landed on the local airport or seaport. The pilot simply tunes-inthe radio station, ascertains the selected course or runway in degrees,sets his desired course index H3 accordingly, and is then prepared toeffect a direct instrument approach and blind descent to the runway. Thenavigation and landing maneuvers are rendered foolproof and saferegardless of wind velocity or other weather conditions.

The basic principal of the indications of the system of the invention isreadily comprehended by the pilot. .It consists in correlating:

1) A course index It held angularly fixed in spaced parallel to thedesired course; with (2) A continuous bearing 20 on a radio station onthe course; together with (3) dlreference index 32 of the aircraftitself.

Each indication may be used independently of the other. However, whencorrelated, they directly and automatically resolve navigation problemsfor the pilot.

Straight track navigation towards a radio station is effected,automatically compensated for drift due to cross-winds, ,by maintainingradio course" index at coincident with desired course index it. Theangle which coincident indices i8 and it makes with lubber line 32 isthe drift angle of the aircraft, indicating the attitude of the aircraftwith respect to the course of flight. The pilot, in a similar manner,can fly a predetermined straight track in any radial direction away froma radio station by keeping tail 2t oi the radio course indicatorcoincident with desired course index it.

The three indices tell the pilot the whole story in the simplestpictorial terms. Interpretation of the readings is practicallyintuitive. All navigational maneuvers are performed by the pilot with aminimum of calculation or interpretation. Only a single ground radiotransmitter is necessary to complete the whole system, which station maybe a commercial broadcast station, simple voice transmitter, Coast Guardstation, radio range, etc.

The setting in degrees of desired course" index ill with respect toscale it depends on several navigational factors. The "desired course isidentical in degrees with the magnetic compass eourse for thedestination, in degrees. The primary factor entering into thedetermination .of the "magnetic compass course and the desired course"is the bearing in degrees of the course or destination of flight withrespect to true North. Such true bearing is generally termed the "truecourse. The easterly or westerly magnetic variation, in degrees, for thevicinity, is respectively subtracted from or added to the "true courseto derive the magnetic course." in a similar manner, deviation indegrees of the actual magnetic compass readings from true magneticreadings is used to correct the magnetic course to arrive at the desiredmagnetic compass course or generally termed compass course.

The compass course is the degrees as read on the magnetic compass forstraight alignment to a destination from a given position. Thesignificance and mode of the compass course determination is well knownto those versed in the art of navigation, and is clearly explained inChapter III of the publication Practical Air Navigation by Thorburn C,Lyon of the U. S. Department of Commerce, published in 1939 by the U. S.Government Printing Office, Washington. The desired course index id isadjusted to read t e compass course for the destination, in degrees ondirectional scale it by arresting movement of disk 26 through thepressing of push-button l9 and rotating directional scale it throughcaging knob ill, in the manner already described. After desired courseindex it is set, the reading of directional scale it with respect to thezero index of lubber line 32 is made to correspond identically with thereading on the magnetic compass of the aircraft. The caging knob i1 isthen replaced to its normal operating position and the compositeindicator l oi the invention is in adjustment for the navi- I maintainedcoincident with lubber line" 32, as

shown. Its use in this case, is similar to the regular direction finder.The setting of the "desired course index I8 is When the aircraft passesover and beyond the radio station it is tuned to, the radio course index20, 20' reverses its indication by 180, serving as a marker indicationof the site of the radio station. Fig. 10 illustrates the reversedposition oi. the radio course index, the tail 20' thereof being alignedwith the head of the lubher line 32. Fig. 11 corresponds to homing"flight towards the radio station, similar to Fig. 9, with the desiredcourse" index it at the right of the two aligned indices; Suchrepresentation may well correspond to a cross-wind opposite to that forFig. 9, or to a substantially difierent distance of the aircraft fromthe station, or a changed attitude of approach thereto on homing.

An important feature of the present invention resides in the feasibilityof straight-track navigation towards or away from a desired radiostation in any radial direction. The straight-track navigation iseffected by keeping the radio course index 2d, it aligned with desiredcourse index it, and disregarding their position of alignment relativeto the lubber line 32. In Fig. 12, the alignment of "radio course head20 with the desired course" index it, signifies that straight-tracknavigation is being executed directly towards the radio station on theground. The radio station has a course bearing corresponding to thesetting of the desired course index it on the gyro-scale it, being 40 inthe present case. This 40 setting as the desired course," corresponds tothe desired magnetic compass course as described. It is the true coursebearing (with respect to true north) as obtained on a map, corrected formagnetic deviation (Westerly or easterly) and for magnetic deviation ofthe magnetic compass itself, as is understood by those skilled in theart of navigation. The angle between the lubber line t2 and the twoaligned indices iii, 20 is the attitude of the aircraft in flight alongthe desired straight track path.

In Fig. 12 the attitude of the aircraft is about 20 to the left of itscourse, compensating for cross-wind from the left. By maneuverin hisaircraft to align the radio course and desired course indices id and2!], the pilot automatically assumes the proper drift angle or attitudeof the aircraft, the magnitude and sense of this angle being pictoriallyindicated on the instrument for the pilot. The flight path in Fig. 12 isat the desired radial direction with respect to the radio station, andtowards the station. As the pilot continues to his destination, the"radio course" and desired course indices iii and 20 remain aligned fora straight-track course to the station, straight with respect to ground.The attitude of the aircraft changes in accordance with the changingvelocity of cross-winds, evidenced by the divergence of the lubber line32 from the aligned indices.

When the pilot passes over the radio station on the straight-track path,the radio course index 26, 20' reverses by 180' so that the had 20thereof continues to point to the radio station. In this position, thetall 20 of the radio course index is aligned with the desired course" itas shown in Fig. 13. The angle of drift remains the same, since itrepresents a continuation of the same attitude of the aircraft withrespect to the straight-track path. Fig. 14 shows the indicationsoccurring when straight-track navigation is directly towards the radiostation, with the cross-winds coming from the direction opposite to thatin Figs. 12 and 13, namely from the right. The aircraft is crabbed intothe wind, to compensate for the cross-velocity, resulting instraight-track flight.

The navigational indicator of the present invention is useful for allnavigational maneuvers and problem which may be encountered in private,commercial, military, or naval operations. Its operation requires asimple radio transmitter ground station, enabling the use of any type ofradio transmitter encountered in the course of navigation' This factoradds to the reliability of the navigational guidance with the andflexibility of the system of the present invention under serviceconditions, typical maneuvers and uses thereof are described in thefollowing:

A, Automatic radio direction flatten-When used as ;u automatic radiodirection indicator, "radio course index 20 is correlated with thelubber line 32. The radio course bearings are true azimuthal readings indegrees, quadrantally compensated over the 360 scale. The readings arenot ambiguous, being uni-directional, and accurate within 1 of arc. Thepilot simply tunes-in the desired radio stat on and radio courseindicator 2|! on unit It continuously points out the direct bearing onthe station. Azimuth indicator il may optionally be referred to, since"radio course" index 20, 20 of composite indicator it is geared in amanner to move in exact correspondence with needle I! of azimuthalindicator ii, to give the same radio bearings, as previously described.A preferred direction flnder circuit is that disclosed in my Patent No.2,308,521 referred to, using a wide range of radio frequencies forreception. Radio bearings may be obtained with the system on any type ofradio transmitter. It is impossible to cause bearing errors or reversalof indication due to mistuning. Night effect, static and interferencedue to mountains are nullified due to ready visual integration of theautomatic bearings. "Homing flight to a radio station is effected bykeeping radio course" indicator 20 coincident with lubber line 32, orkeeping indicator It on the zero index of azimuth indicator ll. When theaircraft passes over the tuned-in radio station, a, 180 reversal of theradio course indicators marks the exact spot of the radio transmitter.

B. Gyro-compasss-The gyro-compass scale i8 serves as the usualdirectional gyroscope when referred to lubber line It. It should bechecked every or minutes against the reading of the magnetic compass,using caging mob ii in the usual manner. No additional gyro-compass isnecessary on the aircraft, thus saving the space, weight and cost ofsuch unit. The desired course" index I! is a valuable addition to thegyro-compass, since necessity for interpreting and calculating the usualgyro-compass readings is avoided. The pilot knows immediately thesigniflcance of the positions of the gyro-scale and desired course"index it with respect to ubbe line" 32, directly giving the directionand degrees of right and left deviation of attitude of the aircraft withrespect to the desired course. The perception is direct and pictorlal.Index It is set at the desired magnetic compass course as previouslydescribed, and adords the pilot a direct interpretation of the attitudeof the aircraft with respect to his chosen course. The feature of theadjustable "desired course index Ill with respect to the directionalscale It referring to the zero index of the indicator may be used napplications independently of the addition of the radio course" index20, iii. The directional scale it may be spatiallyoriented througheither the gyro-compass illustrated or a magnetic compass, or through atelemetering arrangement connected thereto.

C. Automatic orientation.-By directly viewing the desired course," radiocourse," and lubber line indices, the pilot automatically obtains adirect pictorial representation of the aircraft orientation and thenavigational maneuvers. The "desired course index it is adjusted andmaintained spatially paralled to the angular course of the destination.The luminous arrow head 20 of the radio course" represents the tower ofthe radio transmitter at the destina tlon. When the radio tower index itis directly opposite the desired course" index It, the pilot knows thathe is flying in a straight track over round to the tuned-in radiostation. Converse- 1y, when the luminous tail 2c of the radio course"indicator is aligned with the desired course" index it, the pilot knowsthat he is flying in the predetermined radial direction, but directlyaway from the radio station. An angular divergence between radio course"indicator 20 and desired course" indicator it directly informs the pilotof his relative lateral orientation, so that he may directly maneuverthe aircraft in a desired direction. The lubber line 32 together withthe aircraft picture it, when viewed with the other indications l8 andill, gives the attitude of the aircraft with respect to both the"desired course" as well as with respect to the "radio course. The angleof drift due to crosswinds is also directly ascertained from thesereadings.

D. Automatic drift cmnpensation.-'I'he pilot may fly in a straight pathtowards or from a radio station, in any desired angular relation, bykeeping the "desired course" index it aligned with the "radio course" 20and disregarding "lubber line 32. The angle between the lubber line" 32and the aligned indices l8 and 2|], is the angle of drift due to windforces on the aircraft flying in a desired path to the radio station.The attitude which the aircraft must assume to directly fly the desiredangular course with aligned indices IB and 20, automatically results indrift compensation. The drift angles are in turn directly indicated onthe composite indicator.

asaass'r E. Straight track navigation-With the indicator oi theinvention, the pilot can fly by dead reckoning," making good apredetermined track over the ground regardless of wind force ordirection, on any computed radial heading towards or away from a radiostation. The radio station on the desired course is first tuned-in onthe automatic direction finder unit l to control radio course" indexN-W'. The desired course" index it is then adjusted by means of c knobill and push-button N to point to the corrected desired angular courseon gyro-scale II. For straight track flight. towards the radio station,the pilot maintains luminous radio course" head it aligned with luminous"desired course bar it as described in connection with Figs. 12 to it.Cross-winds tend to move these indices apart. By maneuvering theaircraft to keep indices II and ill aligned, the pilot automaticallycorrects for the winds and keeps the straight course with respect toground. When the aircraft passes over the station, luminous head itreverses by 180, the luminous tail til of the radio course indicatormoving opposite luminous bar it as shown in Fig. 13. Straight trackflight may be effected in a direction away from the radio sta-' tion, bymaintaining indices it and it in alignment. Thestraight-track navigationis eguivalent to radio range flight. However, with the system of theinvention no ambiguity whatever is possible, any available type of radiostation may be used for straight tracking, and any desired radialdirection for the straight track it be chosen with respect to thestation.

F. itinerant pilot navigation-With the navigational indicator described,the itinerant pilot may safely fly cross-country on any desireditinerary. He may chart a zig-zag course, referring to any type of radiostation en route. Homing or straight track navigation towards or fromthe radio stations is available. He receives a direct indication.whenever he passes over a chosen radio station in his path. The wideradio irequency range provided increases the usefulness of the systemfor out-of-the-way locations. Cross-country flight for even the noviceis greatly simplified, since his navigation problems are solved by thepictorial indications provided. Also, low approach and blind landingwith the system is rendered a simple maneuver, readily mastered by theveteran pilot and novice alike.

G. Radio range navigation.Navigation on the AN type beacons, known asradio ranges, is a direct, certain and simple matter with the compositeindicator of the invention. No uncertain aural compromises arenecessary. It is practically impossible to get lost with respect to theranges. Should the pilot lose a leg of the beam, the indicatorimmediately informs him just how far off he is, and which way to head toget back on it. It also informs him when he passes over the cone ofsilence of the beacon transmitter onto another leg of the beam, making aspecial Z-type marker beacon for the cone of silence unnecessary. Thedangers attendant the neglect of drift or night efiect in range flyingare'eliminated. Where a squeezed beam is flown against a substantialcross-wind, uncertainties of position or as to which leg of the beam isbeing flown are entirely resolved. The pilot may listen to the ANsignals through the ear-phones if he so desires. The indications, withradio course" index 2!] continuously pointing to the beacon tower, andwith the desired course" index it continuously indicating the angulardirection of the leg of the beam being flown, removes all doubt anduncertainty from beam flying under any condition.

a H. Airline navigation-With the composite navigational indicator,comses may be charted for airliners along any desired region, withoutrequiring special radio ground equipment, station markers or landingglide paths. Advantage may be taken of any type of radio station alongthe course. The system may be used to either "home" or straight track tothe stations, or to fly radio ranges. Marker indications upon passageover any radio station tuned-to is afforded. Automatic compensation fordrift due to crosswinds is available. Mental ease and confidence, and aminimum of calculation for the pilot adds greatly to the desired safetyfor airline operations. Adverse weather conditions, static, night effector mountainous terrain do'not affect the accuracy or performance of thesystem in navigation. The advantages 0:! simplified and foolproofnavigation are equally available to ocean clippers and land lines.Should unexpected divergence from a chosen course be indicated, thepilot may safely navigate to any out-of-the-way locality having anysimple radio transmitter, and readily efiect a blind landing on itslocal airport. Also, lateral separation of aircraft enroute is madepractical.

1. Military maneuver.--Practically every type of military maneuver andoperation may be directly and effectively carried out, with completeassurance and a minimum of calculation by depending on the indicator ofthe invention. Flight to an enemy objectivemay be performed in badweather by relying only on a single transmitter of known position.Homing, straight track flight, gyro-compass indication, station-positionmarking, low approach and blind landing are all available with theinvention instrument, tuned to a single radio station. Problems ininterception, search patrol, aerial survey are greatly simplified. Withthe navigational system of the invention, the military pilot may betterconcentrate on his usual other duties. A typical military aviationproblem is illustrated in Fig. 15, as executed with the indicator of theinvention. A'bombing objective O is in enemy territory across a river.Its course from known friendly radio transmitter T is A cross-wind isblowing as indicated. The pilot flys to station T either by homing alongpath A or straight tracking on the known course to the station alongpath A. The drift angle of the plane is indicated by the lubber lineindication. When the plane passes over station T, the radio course indexreverses The pilot then adjusts the desired course index for the 75objective course, turns about at 1B, and then flys directly towardsobjective 0. The relative indications for this maneuver are shown at C.Drift compensation is efiected for t e straight track. The onlycalculation is for elapsed time to reach objective 0, using the knowndistance from station T, and the air speed of the aircraft.

J. Seaplane landing-The landing of a large seaplane, such as a clippership, or a military or cated to the pilot of the seaplane. The boat ispositioned so that the path of the plane intothe-wind also avoids alllocal obstructions, such as buildings 0. The transmitter T may becarried by a motor truck which may ride to an appropriate position alongthe shore. The pilot adjusts the desired course index in accordance withthe wind direction as ascertained from station T or on the plane itself.He then maneuvers his craft to a position behind the transmitter Tcorresponding to the position shown at A. He knows he is on-course bythe alignment of the radio course" and "desired course indices, as shownin A. In view of the flight being intothe-wind, no drift or crab angleoccurs, as the lubber line shows. The altitude of the aircraft aboveground is then arranged in accord ance with the desired low approachprocedure for the landing of the particular craft. The pilot knows theinstant he passes above transmitter T by the reversed indications of theradio course" index. The pilot gradually descends, passing position 13where the radio course index is 180 away from the "desired course index,and alights on the bay at a position such as indicated at I.

K. Low approach and blind landing.-The system of the invention permits adirect approach to the vicinity of an airport and the confidentmaneuvering of the aircraft to a head-on position to a selected runwayand descent thereon. The system is admirably suited for suchmaneuvering. Fig. 7 diagrammatically represents a. recommended lowapproach and blind landing maneuver. The pilot tunes-in to the radiotransmitter station at the airport, such as transmitter T indicated. Hecommunicates with the airport to find out which runway they recommendusing for landing at that time, in view of traffic or weatherconditions. The selected runway R of Fig. '7 is an 89 course. The pilotthen adjusts the desired course index of the invention unit tocorrespond to the course of the runway, 89 in the present case.Naturally, compensation for a magnetic variation and deviation is madefor the "desired course setting. The transmitter T may be mounted on amotor truck as indicated and is moved in line with the selected runway Rspaced at a predetermined distance from the head of the runway, such as500 feet.

From his original high altitude, such as 3,000 to 10,000 feet atposition A, the pilot flies towards the transmitter T by homing or bystraight track flight as preferred. In homing the lubber line is merelykept coincident with the radio course indication. At position B, thepilot is pretty close to the position of transmitter T and has descendedto 2,000 feet elevation, The pilot knows as soon as he passes over thestation T by the reversal of the radio course indication. When he passesstation T, he makes a turn as indicated at position and moves hisaircraft on-course" with the runway as denoted by the alignment of the"radio course index with the desired course index. The present case isillustrated without cross winds. The elevation of the aircraft isgradually reduced. At position D, it is at 1,500 feet, and on-coursewith runway It still flying away therefrom. The pilot continues to flyaway from station T for about three minutes as reckoned from hisposition at C before attempting to reverse his flight and effect theblind landing. The fan marker beacon indicated in dotted may opasaasa'ztionally be located about 10 miles from the runway to inform the pilotwhen to effect such turn.

At position E, the pilot is ready to execute a. standard 180 turn, stillreducing altitude. At position F, the elevation is about 1,000 feet andthe aircraft is directed to the on-course 89 path to runway R. Theaircraft is on-course again at position G and its elevation, in thiscase, is preferably about 800 feet above ground. Flight is continued toposition H near the head of transmitter T, lowering the elevation untilit is about 200 feet at that position, and at the same time lowering thespeed of flight oi. the aircraft. The pilot knows when he passes overstation 'I' by the reversal of the radio course index. At this time, heis ready to effect a blind descent to the runway R. His descent rateshould be about 300 to 400 feet per minute at aircraft speed of 75 to 85miles per hour.

In view of the accurate radio and "desired course indications of thesystem, the runway locallzer action for blind landing is possible foreven a relatively narrow runway. The efiects of cross-winds areautomatically compensated for by adjustment of the plane into a propercrabbing angle. Thus, in conjunction with a sensitive altimeter, thesystem of the invention efiects automatic low approach and blind landingwith a single transmitter T placed at the head of the rimway asindicated. Two-way radio communication is constantly elfectedwithstation T, which may be voice modulated from a control tower of theairport or by an operator in a vehicle.

Having thus described the present invention in connection with preferredexempliflcations thereof, it is to be understood that constructionalmodifications are feasible within the broader spirit and scope of theinvention, and that the system of the invention may be used fordifferent maneuvers and other purposes than those referred to, forexample aboard marine craft. Accordingly it is not intended to belimited except as set forth in the following claims.

Iclaim:

1. A vehicle navigational instrument of the character describedcomprising a rotatable radio course index, directional compass meanshaving coupled thereto a turn-table, a toothed disk with a desiredcourse index, said disk being rotatable by and adiustably mounted onsaid turn-table and arranged coaxially with said radio course index,mechanism operable from the exterior of said instrument for selectivelyengaging said toothed disk to arrest the position thereof, and a devicecoupled to said directional compass means and operable from the exteriorof said instrument for manually rotating said turn-table, whereby therelative setting of said desired course index with respect to saidturn-table is manually controllable when said mechanism is engaged withsaid disk.

2. In a vehicle navigational instrument of the character describedcomprising a rotatable radio course index, gyro-compass means havingcoupled thereto a turn-table, and a disk rotatable by and adjustablymounted on said turn-table arranged coaxially with said radio courseindex and having a desired course index in the form of a luminouscompound marked thereon, and a corresponding region diametricallyopposite said desired course index symmetrically containing anequivalent form of luminous compound to compensate the action of saidgyro-compass means against precessional errors due to moistureabsorption by the luminous compound. A

3. A navigational instrument of the character described comprising: adirectional compass, a disk containing a desired course index, said diskbeing rotatable by and adjustably mounted on said directional compass, amember rotatably supported adjacent said disk, a radio course indexcarried by said member coaxially and simultaneously visible with saiddesired course index, a housing for said directional compass andindices, an element rotatably supported in said housing, said elementbeing engaged with said member for rotation thereof and having aprojecting portion for external mechanical coupling, mechanism mountedin said housing adjacent said disk and arranged for direct contactingengagement with said disk, and means for turning said compass while saidmechanism is held in engagement with said disk for shifting the angularposition of said desired course index with respect to said compass.

4. A navigational instrument of the character described comprising: adirectional compass, a turn-table coupled thereto, said turn-table beingspatially oriented by said directional compass, a disk containing adesired course index, said disk being rotatable by and adjustablyarranged on said turn-table, a member rotatably supported adjacent saidturn-table, a radio course index carried by said member coaxially andsimultaneously visible with said desired course index, a housing forsaid directional compass and indices, an element rotatably supported insaid housing, said element being coupled to said member for rotationthereof and having a projecting portion for external mechanicalcoupling, mechanism mounted in said housing adjacent said disk andarranged for direct contacting engagement with said disk, and means forturning said turn-table while said mechanism is held in engagment withsaid disk for shifting of the angular position of said desired courseindex on said turn-table.

5. A navigational instrument of the character described comprising: adirectional compass embodying a turn-table which bears a three hundredand sixty degree scale, said turn-table being spatially oriented by saiddirectional compass, a disk containing a desired course index coaxiallyarranged on said turn-table and adjustably mounted thereon, a gearmember rotatably supported adjacent said disk, a radio course indexcarried by said member coaxially and simultaneously visible with saiddesired course index, a

housing for said directional compass and indices,

a gear element rotatably supported in said housing, said gear elementmeshing with said gear member and having a portion extending through thehousing for external mechanical coupling thereto, mechanism mounted insaid housing adjacent said disk and arranged for direct contactingengagement with said disk for selective manual shifting of the angularposition of said desired course index on said turn-table, a windowmounted on the housing over said indices, and a stationary referencecourse index arranged on said window in a radial direction parallel withthe other indices when in alignment therewith.

. 6. A navigational instrument of the character described comprising: adirectional compass, a disk containing a desired course index, said diskbeing rotatable by and adjustably mounted on said directional compass, amember rotatably supported adjacent said disk, a radio course indexcarried by said member coaxially and simulplunger mounted in saidhousing substantially in the plane of said disk and having a tipprojecting thereto for direct engagement'therewith, and a springconnecting to said plunger for normally holding said tip disengaged fromsaid disk.

7. A navigational instrument of the character described comprising: anair-driven gyro-compass embodying a turn-table having a three hundredand sixty degree scale, said turn-table being spatially oriented by saidgyro-compass, a disk containing a desired course index, said disk beingrotatable by and concentrically arranged with said turn-table andadjustably mounted thereon, a gear member supported adjacent said disk,a

"radio course index carried by said member coaxially and simultaneouslyvisible with said desired course index, a housing for said gyro-compassand indices, a gear element rotatably supported in said housing, saidgear element meshing with said gear member and having a projectingportion extending through the housing for external mechanical coupling,and a window sealed in the housing above said 'indices,' a stationaryreference course index marked on said window, and mechanism for directcontacting engagement with said disk for selective manual shifting ofthe angular position thereof on said turn-table comprising a plungermounted in said housing having a tip projecting towards the periphery ofsaid disk, 9. part of said plunger extending exteriorly of said housingfor manual actuation, and an air-tight packing slidably sealing saidplunger in said housing.

8. A vehicle navigational instrument of the character describedcomprising a rotatable radio course index, directional compass meanshaving coupled thereto a turn-table, a disk with a desired course index,said disk being rotatable by and adjustably mounted on said-tum-tableand arranged coaxially with said radio course index, mechanism operablefrom the exterior of said instrument for selectively engaging said diskto arrest the position thereof, and a device coupled to said directionalcompass means and operable from the exterior of said instrument formanually rotating said turn-table, whereby the relative setting of saiddesired course index with respect to said turn-table is manuallycontrollable when said mechanism is engaged with said disk.

9. A vehicle navigational instrument of the character describedcomprising a rotatable radio course index, directional compass means, aturntable, and telemetering mechanism coupling said directional compassmeans to said turn-table, a disk with a desired course index, said diskbeing rotatable by and adjustably mounted on said turn-table andarranged coaxially with said radio course index, mechanism operable fromthe exterior of said instrument for selectively engaging said disk toarrest the position thereof, and a device coupled to said directionalcompass means and operable from the exterior ,of said instrument formanually rotating said turn-table, whereby th relative setting of saiddesired course index with respect to said turn-table is manuallycontrollable when said mechanism is engaged with said disk.

10. In a vehicle navigational instrument of the character describedcomprising a rotatable radio course index, gyro-compass means havingcoupled thereto a turn-table. and a disk rotatable by and adjustablymounted on said turn-table arranged coaxially with said radio courseindex and having a desired course index in the form of a luminouscompound marked thereon, and a corresponding region diametricallyopposite said desired course index symmetrically containing anequivalent form of luminous compound to compensate the action of saidgyro-compass means against precessional errors due to moistureabsorption by the luminous compound, mechanism operable from theexterior of said instrument for selectively engaging said disk to arrestthe position thereof,

and means for turning said compass while said mechanism is held inengagement with said disk for shifting the angular position of said diskwith respect to said turn-table.

11. A vehicle navigational instrument of the character describedcomprising a rotatable radio course index, directional compass meanshaving coupled thereto a turn-table, a disk with a desired course index,said disk being rotatable by and adjustably mounted on said turn-tableand arranged coaxially with said radio course index,

electrically operable mechanism controlled from the exterior of saidinstrument for selectively engaging said disk to arrest the positionthereof, and a device coupled to said directional compass means andoperable from the exterior of said instrument for manually rotating saidturn-table, whereby the relative setting of said desired course indexwith respect to said turn-table is manually controllable when saidmechanism is engaged with said disk.

12. A navigational instrument of the character described comprising: adirectional compass, a disk containing a desired course index, said diskbeing rotatable by and adjustably mounted on said directional compass, amember rotatably supported adjacent said disk, a radio course indexcarried by said member coaxially and simultaneously visible with saiddesired course index, a housing for said directional compass andindices, an element rotatably supported in said housing,

said element being engaged with said member for rotation thereof andhaving a projecting portion for external mechanical coupling, andmechanism for direct contacting engagement with said disk for selectivemanual shifting of the angular position of said desired course indexwith respect to said compass comprising a plunger substantially in theplane of said disk and having a tip pro- Jecting thereto for directengagement therewith, a solenoid supported in said housing and meetablewith said plunger, said solenoid being operable when energized to urgesaid plunger towards said disk, a spring operatively associated withsaid plunger for normally holding said tip disengaged from said disk,and means on the exterior of said housing for energizing said solenoid.

13. A navigational instrument of the character described comprising: anair-driven gyro-compass embodying a turn-table having a three hundredand sixty degree scale,\said turn-table being spatially oriented by saidgyro-compass, a disk containing a desired course index, said disk beingrotatable by and concentrically arranged with said turn-table andadjustably mounted thereon, a gear member supported adjacent said disk,a radio course index carried by said member coaxially and simultaneouslyvisible with said desired course index, a housing for said gyro-compassand indices, a gear element rotatably supported insaid housing, saidgear element meshing with said gear member and having a projectingportion extending through the housing for external mechanical coupling,and a window sealed in the housing above said indices, a stationaryreference course index marked on said window, and mechanism for directcontacting engagement with said disk for selective manual shifting ofthe angular position thereof on said turn-table comprising a plungermounted in said housing having a tip projecting towards the periphery ofsaid disk, a solenoid connected to said plunger and operable whenenergized to urge said plunger toward said disk, a spring operativelyassociated with said plunger for normally holding said tip disengagedfrom said disk, and control means for energizin said solenoid sealed insaid housing and operable from the exterior thereof.

WILLIAM P. LEAR.

